Cuvette, Insert, Adapter and Method for Optically Examining Small Amounts of Liquid

ABSTRACT

Cuvette, comprising at least one measuring area on each one of two arms that are pivotally connected to each other such that from a swung-apart condition, they can be swung together into a measuring position in which the two measuring areas have a distance for positioning a sample between the measuring areas, and means for positioning the two arms in a measuring position in a cuvette shaft of an optical measuring device with a sample between the two measuring areas in a beam path of the optical measuring device that crosses the cuvette shaft.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not applicable.

BACKGROUND OF THE INVENTION

The present invention is related to the analysis of liquid samples witha spectrometer or photometer or other optical measuring devices. Suchanalyses are made typically, but not exclusively, in themolecular-biological, biochemical, inorganic-chemical, andorganic-chemical and foodstuff chemical laboratory. Samples areoptically analysed for instance in research, in diagnostics and inquality control. They are analysed for instance by way of absorption-,reflection-, emission-, fluorescence-, Raman- or luminescencespectroscopy in the UV-VIS or IR wavelength range. Examples for analytesto be measured are biomolecules like nucleic acids, proteins, lipids aswell as inorganic or organic materials and compounds. These analytes canbe measured directly or after a chemical reaction that serves forfacilitating the spectrometric or photometric analysis.

The present invent is related in particular to all the applications thatwere mentioned by way of example above. An essential field of itsapplication is the measurement of valuable samples in small amounts inmolecular biology. Often only small amounts of sample are at hand (forinstance, from less than 1 up to 5 micro-litres), because nor morematerial can be obtained. When diluting the samples, the measurementresults would become too inaccurate due to decreased absorption. Atypical application is the photometric or fluorometric measurement ofnucleic acid concentrations before a PCR or real-time PCR, in order tobe able to use that starting amount of the nucleic acid which is optimumfor PCR. Another example is the measurement of the concentration ofnucleic acids and marker substances incorporated into the nucleic acid,as well as of the marking density of marked nucleic acids derived fromthis, in order to be able to use the optimum amount of marked nucleicacid before beginning a micro array experiment, and to be sure that themarking density of the nucleic acid is in the optimum range.

For spectrometric or photometric analysis, liquid samples are filledinto cuvettes. Standard cuvettes are suited for the insertion into thecuvette shafts of most of the current spectrometers and photometers.These cuvette shafts are also called “standard cuvette shafts” in thefollowing. Standard cuvette shafts of usual commercial optical measuringinstruments having a cross section of 12.5 mm×12.5 mm have becomewide-spread. The heights of the light beam above the bottom of thecuvette shaft vary from 8.5 mm to 20 mm, depending on the type of thedevice. Standard cuvettes have a box-like outline, wherein the crosssection and the height are matched to the dimensions of the standardcuvette shafts.

Re-usable standard cuvettes of quartz glass for small amounts of sampleare marketed by the companies Hellma and Starna in particular. Theseultra micro cuvettes have a layer thickness of 1 mm or more. It is verydifficult to fill them without bubbles, and very sumptuous to empty andto clean them. Because the main application of the optical measurementsis the measurement of very small volumes when measuring nucleic acids inthe UV region, they are made of quartz glass and are particularlyexpensive. They must be treated with much care, because they are veryexpensive to buy. For the ultra micro cuvettes of quartz glass that areobtainable on the market, a minimum volume of 5 micro-litres must beused, which is too much for many applications.

Other cuvettes are marketed with the designation “Mikroliter-Messzelle”(micro-litre measuring cell). Under the product name “Tray Cell®”, thecompany Hellma, and under the product name “Label Guard” the companyImplen markets a micro-litre measuring cell which corresponds to astandard cuvette in its dimensions, and may therefore be used in many ofthe today's spectrometers. The micro-litre measuring cell of the companyHellma is described in WO 2005/114146 A1. In order to make an analysis,one drop of about 1 to 2 micro-litres of the liquid to be analysed mustbe applied to the topside of a measuring window at a layer thickness of0.2 mm, or at a layer thickness of 1 mm when the drop is 3 to 5micro-litres. The measuring chamber is closed by a lid. The light beamof the measuring optics is guided from the radiation source through thesample to the sensor via beam deflections and fibre-optic light guidesand via a mirror in the lid.

The micro-litre measuring cell is very sumptuous in its construction andit has a high price, and therefore it cannot always be used in aneconomically reasonable fashion. Moreover, it has a highapparatus-dependent intrinsic absorption of 1,3 E at 230 to 650 nm,about which the measurement range of the measuring instrument isreduced. Further, it is not possible to visually check the measuringsolution in the measurement chamber after filling in the sample andputting up the lid, in order to detect disturbing bubbles, particles anderroneous pipettings that might lead to erroneous measurements. Inaddition it is disadvantageous that the user must clean the measuringwindow after use in a time-consuming way.

Under the product name “Nano Quant Plate”, the company Tecan offers akind of collapsible micro-plate for a micro-plate reader.

Under the product name “NanoDrop®”, the company NanoDrop Technologiesmarkets a photometer, which permits to analyse samples that have avolume of one micro-litre only. This spectrometer is described in WO2006/086459 A2. The system envisions the direct optical measurement in adrop of liquid which is located between two horizontally aligned, planarsurfaces. A light source illuminates the sample of liquid from the sidethrough the gap between the two surfaces. A fibre light guide runs outinto the lower surface, which leads the light further to a fibre opticsspectrophotometer after it has passed through the liquid sample. Thus,the sample liquid is in direct contact with the glass fibre.

In the spectrophotometer, it is disadvantageous that the optical surfacecan be negatively affected by certain samples. According to theoperation manual of the spectrophotometer of the type NanoDrop-1000,such samples are for instance protein containing solutions. In thiscase, the user must manually condition anew the optical surface afterrepeated usage by intense, time-consuming strong rubbing. Also, stronglyacidic or alkaline solutions cannot be used.

Further, the sample is in direct, open contact with the solution. Thus,dangerous substances cannot be examined with this system. However,dangerous materials, like possibly infective substances, are often usedin the molecular-biological, cell-biological, biochemical and chemicallaboratory. The system is not suited for these samples. Due to the opencontact of the sample with the surroundings, samples may becomecontaminated. This may disturb the measurement. Moreover, it is notpossible to re-obtain valuable samples after the measurement without therisk of contamination.

The spectrophotometer is a very expensive measuring system. It comprisesa measuring unit and a PC and consumes much space. The sample mayquickly evaporate and easily become contaminated, because the surfacearea of the open drop of liquid has direct contact to the surroundings.

BRIEF SUMMARY OF THE INVENTION

Starting from this, the present invention is based on the objective toprovide a device that is suited for the optical examination of smallamounts of sample with high precision, using conventional opticalmeasuring devices.

Further, a method is to be provided which permits the opticalexamination of particularly small amounts of sample.

This objective is achieved by a cuvette according to claim 1.Embodiments of the cuvette are indicated in subclaims.

The objective is further achieved by an insert according to claim 18 andan adapter according to claim 20. Embodiments of insert and adapter areindicated in other subclaims.

Finally, the objective is achieved by a method according to claims 35,37 and 39. Embodiments of the methods are indicated in furthersubclaims.

The cuvette of the present invention comprises at least one measuringarea on each one of two arms that are pivotally connected to each other,such that from a swung-apart condition, they can be swung together intoa measuring position in which the two measuring areas have a distancefrom each other for positioning a sample between the measuring areas,and means for positioning the two arms in the measuring position in acuvette shaft of an optical measuring device with a sample between thetwo measuring areas in a beam path of the optical measuring device thatcrosses the cuvette shaft.

According to one embodiment, a cuvette of the present inventioncomprises at least one measuring area on each one of two arms that arepivotally connected to each other, preferably by way of an articulation,such that from a swung-apart condition, they can be swung together intoa measuring position in which the arms can be positioned in a cuvetteshaft, and the two measuring areas face each other and have a distancefrom each other. As means for positioning, this embodiment has a form ofthe arms swung together in the measuring position that matches thecuvette shaft. This cuvette is adapted to the cuvette shaft by the formof the arms swung together, so that a sample held between the measuringareas is disposed in the beam path when the cuvette is put into thecuvette shaft. As a consequence, the arms of this cuvette are alsodesignated as “adapter parts”, or both arms together as “adapter” in thefollowing.

According to another embodiment, a cuvette of the present inventioncomprises at least one insert with two measuring areas and an adapterfor insertion into a cuvette shaft of an optical measuring device, andmeans of insert and adapter for detachably holding the at least oneinsert on the adapter, the measuring areas being in a distance from eachother, for positioning a sample between the measuring areas in a beampath of the optical measuring device that crosses the cuvette shaft.

In this embodiment, the adapter has a shape matched to the cuvetteshaft, so that a sample held between the measuring areas of the insertis disposed in the beam path when the insert is put into the adapter andthe adapter is set into the cuvette shaft.

A preferred embodiment features means for positioning the two armsdisposed in the measuring position in a standard cuvette shaft. Astandard cuvette shaft in the spirit of the present invention has arectangular, in particular square cross section. According to oneembodiment, it has a bottom area of 12.5×12.5 mm. According to a furtherembodiment, the beam path runs in a distance of 8.5 mm to 20 mm abovethe bottom of the cuvette shaft. According to a further embodiment, thebeam path runs in a distance of 8.5 mm or 15 mm above the bottom of thecuvette shaft. The cross section of the cuvette, for instance the crosssection of the swung together arms or the cross section of the adapterfor receiving the insert, is matched to the cross section of thestandard cuvette shaft. According to one embodiment, the measuring areasare positioned such in the cuvette that their centre has theabove-mentioned distance of the beam path from the bottom of the cuvetteshaft.

According to one embodiment, the cuvette has means for positioning thetwo arms disposed in the measuring position in different positions in acuvette shaft. According to further embodiments, these are means forpositioning in different heights and/or different horizontal positionsin the cuvette shaft. The means may for instance be feet of the cuvettethat can be drawn or screwed outward, or they may be realised by anasymmetrical arrangement of the measuring areas in connection with anarrangement of the cuvette in different rotational positions in thecuvette shaft. For instance, they serve for the adaptation to the heightof the beam path of the measuring device, or for measuring differentsamples on the measuring areas of one cuvette in the same measuringdevice.

In the spirit of the present invention, a cuvette is a device which isdestined to position samples for optical examinations. Thus, a cuvetteof the present invention has not to be realised in a conventional manneras a vessel with an accommodation for liquids that is enclosed by bottomand side walls, such a realisation being not excluded at all, however.

In the cuvettes of the present invention, a small volume of a liquidsample is positioned between the two measuring areas. A column betweenthe two measuring areas is formed by the surface tension of the liquid,through which an optical measurement can be performed. The adapterserves to position the measuring areas in a preferably verticalalignment such in the cuvette shaft, that it can be measured in aconventional photometer or spectrometer without further alterations ofthe light path. For this purpose, the adapter is preferably matched tothe dimensions of a standard cuvette shaft, so that it can be insertedlike a standard cuvette. But however, the adapter can also be matched toa cuvette shaft with other dimensions than a standard cuvette shaft.

The insert and/or adapter may be realised for multiple use or as aconsumable or disposable item for single use. The insert and/or theadapter may be made of one or plural plastics and/or of one or differentmaterials. Insert and adapter can alternatively be fixedly connected, orconsist of one single device, respectively.

The insert and/or the adapter is for instance made of metal (likealuminium or stainless steel, e.g.), and/or of one or plural plastics orhard plastics or soft plastics, respectively (for instance polystyrene,PVC, polypropylene, polyethylene). The measuring areas or insert partsthat have the measuring areas are for instance made of transparentplastics (for instance Topas or polystyrene), quartz glass or anotheroptically transparent glass (for instance BK 7). For measuring nucleicacids, a combination of an adapter of aluminium with measuring areas orinsert parts, respectively, of quartz glass is well suited inparticular.

Alternatively, the measuring areas may also be realised such thatseveral samples can be arranged on them, for instance by correspondingsurface shaping. The samples may be different or be applied on themeasuring area as identical samples.

According to possible embodiments, the two measuring areas are arrangedon two arms of an insert, of a pincette in particular, or on two adapterparts of an adapter realised as a collapsible device, by the aid ofwhich a sample arranged between the two measuring areas can be alignedin the measuring direction. In this, the two measuring areas can beconnected in one piece with the two arms or adapter parts, which ontheir turn can be connected with each other by being one piece. When thearms or adapter parts are swung apart, the measuring areas stand onetowards the other such that a sufficiently great free space is providedfor applying the liquid sample, for instance in the form of a drop. Thesample can be applied to only one or to both measuring areas. Byswinging the two arms or adapter parts together, it is achieved that themedium wets both measuring areas and a column of liquid is formed therebetween. Alternatively, the liquid may also be applied directly into agap between the two measuring areas, so that a relative movement of themeasuring areas towards each other can be omitted. For this purpose, theliquid can be put in between measuring areas that are movable withrespect to each other and which were set to a suitable distance fromeach other. Further, for this purpose the liquid can be put between twomeasuring areas which have a stationary, fixed distance from each other.

Measurements with volumes from less than one micro-litre up to severalmicro-litres can be realised in one cuvette by distances of differentmagnitude between the two measuring areas. According to a preferredembodiment, the distances between the two measuring areas aredimensioned such that samples with volumes in the range of 0.2 to 5micro-litres can be held there between. Further preferred, the distancesbetween the measuring areas are dimensioned such that the volumes of thesamples that can be held between them amount to about 1 to 3micro-litres. Thus, the cuvette can be dimensioned for a certain volume,wherein the measuring areas can be held in the beam path only in acertain distance from each other.

Positioning a liquid sample on one of the two measuring areas, forinstance of an insert or a collapsible device, can take place with theaid of a pipette. In this, the pipette can be set onto the measuringarea with or without a guide device. After delivery of the necessaryamount of sample, the arms of the pincette or collapsible device areswung together.

After application of the sample, an insert can be set into an adapterand it can be positioned in a vertical alignment in a cuvette shaft.

An insert of the present invention for an adapter that is insertableinto a cuvette shaft of an optical measuring device has two measuringareas and means for holding on the adapter, the measuring areas being ina distance from each other, in order to position a sample between themeasuring areas in a beam path of the optical measuring device thatcrosses the cuvette shaft.

The means for detachably holding the insert can be in particularcontours or an outer geometry of the insert, respectively, which ismatched to a contour or respectively geometry of the adapter, so thatthe insert can be joined to the adapter.

The insert of the present invention may advantageously have one orplural features of the insert of the cuvette of the present inventionexplained above, which comprises at least one insert and an adapter.

An adapter of the present invention for at least one insert having twomeasuring areas can be put into the cuvette shaft of an opticalmeasuring device and has means for detachably holding the at least oneinsert, the measuring areas being in a distance from each other, inorder to position a sample between the measuring areas in a beam path ofthe optical measuring device that crosses the cuvette shaft.

The adapter of the present invention may advantageously have one orplural features of the adapter of the cuvette of the present inventionexplained above, which comprises at least one insert and an adapter.

The means for detachably holding the adapter can be in particular acontour or respectively geometry of the adapter, which is matched to acontour or respectively geometry of an insert, so that the adapter canbe joined to the insert.

A collapsible device of two arms or respectively adapter parts that areconnected by an articulation has the shape of a common commercialcuvette when the two adapter parts are swung together. The measuringareas can be present in particular on replaceably installed insert partsof quartz glass or plastics. Further, they may be connected to the armsor respectively adapter parts as being one piece and/or in a notdetachable fashion. For instance, the arms with the measuring areas aremade as one piece of plastics. In this, the arms are connected to eachother preferably as being one piece, for instance via a film hinge.Insert parts of quartz glass or replaceable insert parts of plastics canin particular be present in cuvettes for multiple use. Collapsiblecuvettes for multiple use may in particular feature arms or respectivelyadapter parts of metal. An arm or respectively an adapter part of metalor of another material that is not optically transparent (for instanceof an opaque plastics) can be realised as a stop for limiting the lightpassage through the measurement volume.

A collapsible cuvette can be made of plastics or another material formulti-use or as a disposable item for single use. The two adapter partscan be connected articulately with each other via a film hinge, or eachmay have articulation parts which are mutually connected to a joint. Theadapter parts can serve as stops for shielding the measurement volumeagainst excess light. For this purpose, the adapter parts may consistentirely or partly of coloured plastics, or they may wearlight-impermeable coatings. For instance, the collapsible cuvette hasadapter parts of UV-impermeable plastics and inserts of UV-transparentplastics.

According to one embodiment, there are means for detachably locking thetwo adapter parts in the measuring position. These may be incorporatedmagnets, in adapter parts of metal in particular. Elastic catching hooksthat co-operate with catching edges may exist in adapter parts ofplastics in particular. The catching hooks and catching edges can bemade in one piece with the adapter parts of plastics.

In all the variants of the present invention mentioned above, the beampath of the optical measuring device may run crosswise through themeasuring areas, for which purpose the measuring areas or respectivelythe insert having the measuring areas are realised as being transparentor clear or optically diaphanous, respectively. According to anotherembodiment, the beam path of the optical measuring device runs inparallel to the measuring areas through open sides of the distanceregion between the measuring areas. In this case, the measuring areasmay also be made light-impermeable. Even though the beam path does notrun across the measuring areas in this embodiment, they are designatedas “measuring areas”, because they position the drop for the measurementin the beam path.

In principle, measuring areas may have a curved one or another shape.According to a preferred embodiment, the measuring areas are planar.When the measuring areas are disposed on the side of an insert part (forinstance, of a platelet) or respectively of a wall, both sides of theplatelet or respectively the wall are preferably planar.

In principle, the planar measuring areas may have any arbitraryalignment to each other. For instance, they may be aligned at an angleto each other. According to a preferred embodiment, the measuring areasare disposed with surfaces parallel to each other. This plane-parallelarrangement of planar measuring areas serves in particular for thepassage of the beam path through the measuring areas without disturbingdeflection of the light beam.

In principle, the measuring areas may have different alignments withrespect to each other, for instance such that the measuring areas occupyangles against each other in all the three spatial axes. According to apreferred embodiment, the measuring areas are disposed such that theycover up each other. Preferably, the measuring areas are present onplane-parallel platelets in an arrangement so as to cover up each other.

According to one embodiment, the distance of the measuring areas fromeach other is 5 mm or less in the measuring position. At the mentioneddistance, many of the liquid samples to be examined are held between themeasuring areas due to capillary forces. The distance is preferably 0.1to 2 mm. Particularly preferred is a distance of about 1 millimetre.

According to a method of the present invention for optically examiningsmall amounts of liquid, two drops of liquid are applied to twopreferably planar measuring areas, the drops are brought into contactwith each other by drawing the two measuring areas near to each other,so that the drops coalesce into one single drop, and this drop issubjected to an optical measurement.

By applying a reduced measurement volume to both measuring areas, andthe subsequent positioning or drawing together of the areas, a volumereduction may be achieved. Namely, the added height of two drops withhalf the volume is greater than the height of one single drop with thewhole volume. Thus, wetting both measuring areas can be achieved with asmaller volume also.

According to a further variant, in a method of the present invention foroptically examining small amounts of liquid, two measuring areasarranged in a distance from each other are simultaneously wetted with aliquid sample, so that the drop is spanned out between the measuringareas through its surface tension, and this drop is subjected to anoptical measurement.

This method of positioning the sample amount upon simultaneous wettingof both measuring areas directly when the sample is applied results alsoin a reduction of the necessary amount of sample. A pipette may be usedin order to position the sample. Guiding the pipette point before andafter the pipetting process may favour this effect.

In all the variants of the present invention, safe and handling-friendlypositioning of drops can be facilitated by guiding the pipette pointwhen picking up and/or delivering the liquid.

The cuvette of the present invention is preferably dimensioned such thatit fits into a standard cuvette shaft as a standard cuvette. But it mayalso be made such that it fits into a cuvette shaft of otherconventional or future optical measuring devices.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings shows:

FIG. 1 a pincette with planar measuring areas at the free ends andopened arms, in a perspective view slantwise from the side;

FIG. 2 the same pincette with arms swung together, in the sameperspective view;

FIG. 3 an adapter with an accommodation for the pincette, in aperspective view slantwise from the topside and from the side;

FIG. 4 the same adapter with inserted pincette, in a perspective X-rayimage;

FIG. 5 a pipette point with planar measuring areas on the lower end, ina perspective view slantwise from the downside and from the side;

FIG. 6 an adapter with an accommodation and the pipette point insertedtherein, in a perspective view slantwise from the topside and from theside;

FIG. 7 the pipette point being inserted into the adapter, in a top view;

FIG. 8 the pipette point being inserted into the adapter, in a sideview;

FIG. 9 a slide with a planar measuring area, in a perspective viewslantwise from the topside and from the side;

FIG. 10 an adapter for accommodating two slides in the opened condition,in a perspective view slantwise from the topside and from the side;

FIG. 11 the adapter equipped with two slides in an unfolded condition,in a perspective view slantwise from the downside and from the side;

FIG. 12 the adapter equipped with the slides in the collapsed condition,in a perspective view on two sides;

FIG. 13 an adapter equipped with insert parts having planar measuringareas, the adapter parts being swung apart, in a perspective viewslantwise from the downside and from one side;

FIG. 13.1 a variant of the adapter with a recess for inserting a pipettepoint with arms swung apart, in a perspective view;

FIG. 14 the same adapter with adapter parts swung together in the sameperspective view;

FIG. 14.1 the same adapter with arms swung together in a perspectiveview;

FIG. 14.2 the same adapter with arms swung together in a side view;

FIG. 15 insert part with planar measuring area having liquid-wetting andliquid-repellent zones, in a view slantwise towards the planar measuringarea and towards the side;

FIG. 16 the same insert part in a perspective view towards the opposingplanar outer side;

FIG. 17 planar measuring area with recess, in a longitudinal section;

FIG. 18 planar measuring area with several overflow chambers in a topview;

FIG. 19 planar measuring area with one overflow chamber in the top view;

FIG. 20 planar measuring area with liquid-wetting centre region andliquid-repellent border surfaces in a longitudinal section;

FIG. 21 planar measuring areas with one drop put up there before drawingthe measuring areas together, in a longitudinal section;

FIG. 22 the same measuring areas after drawing together, in alongitudinal section;

FIG. 23 two planar measuring areas with two drops put up there beforedrawing the measuring areas together, in a longitudinal section;

FIG. 24 the same measuring area after drawing together, in alongitudinal section;

FIG. 25 magnetic locking of two measuring areas in the measuringposition in a longitudinal section;

FIG. 26 cuvette with a capillary channel that is open towards two sides,in a side view;

FIG. 27 the same cuvette in another side view;

FIG. 28 the same cuvette, in a perspective view slantwise from twosides;

FIG. 29 an insert having plural measuring areas, the arms being swungapart, in a perspective view;

FIG. 30 the same insert, put into an adapter, in a perspective view.

DETAILED DESCRIPTION OF THE INVENTION

While this invention may be embodied in many different forms, there aredescribed in detail herein a specific preferred embodiment of theinvention. This description is an exemplification of the principles ofthe invention and is not intended to limit the invention to theparticular embodiment illustrated

In the following, the designations “upside” and “downside” refer to thatorientation which the corresponding parts of the device have when theyare arranged in a cuvette shaft of a photometer or spectrometer.

The cuvette shown in FIGS. 1 to 4 consists of at least two parts.

A device 1 consists of two platelets 2, 3 with planar measuring areas 4,5 on the inner sides, and an adapter 6 for positioning the device 1 in aconventional photometer, spectrometer or the like.

In the example, the platelets 2, 3 of the device 1 are arranged on thefree arms 7, 8 of a pincette 9. In their lower region, the arms 7, 8 arebevelled towards the platelets 2, 3. The arms 7, 8 are preferablyfixedly connected to each other on the upper ends at 10. The arms 7, 8can be elastically swung together. Swinging the arms 7, 8 together islimited by the spacer parts 11, 12 arranged on the inner sides of thearms 7, 8 in the form of two ribs running crosswise to the arms,preferably near to the measuring areas.

The adapter 6 itself has the cuboid-shaped outline of a standardcuvette. In its upper region, it is closed all around, and at the bottomside it has four feet 14 to 17.

The adapter 6 has a cavity 18 in its interior, two parallel guide rails19, 20, 21, 22 for the pincette 9 being arranged in the interior on eachof two opposing side walls.

The pincette 9 can be inserted into the guiding mechanism formed by theguide rails 19 to 22 when the arms are swung together according to FIG.2.

At the downside, the guide rails 19 to 22 are limited by limitationwalls 23, 24 inclined towards the inside, whose inclination correspondsto the inclination of the bevels of the arms 7, 8 of the pincette 9. Atthe inside, the limitation walls 23, 24 project from the side wallswhich bear the guide rails 19 to 22.

A box-like bottom part 25 is inserted onto the lower borders of thelimitation walls 23, 24. This part has passage openings 26, 27 onopposing front surfaces.

Thus, the construction of the adapter 6 corresponds essentially to thecuvette according to the German patent DE 198 26 470 C1, U.S. Pat. No.,6,249,345, the disclosure of which is incorporated herein by reference.The deviations from the known constructions are that the inner sides ofthe side walls are provided with the guide rails 19 to 22, and that thebox-like bottom part 25 has passage openings 26, 27.

The pincette 9 may be realised as a disposable item. The adapter 6 mayalso be a disposable item or it may be re-usable. Pincette 9 and adapter6 are preferably made of plastics.

A small volume of the liquid to be analysed is positioned between theoptically transparent measuring areas 4, 5 of the device 1. The adapter6 serves to position subsequently the device 1 having the planarmeasuring areas 4, 5 in a vertical alignment such in a cuvette shaftthat it can be measured in a conventional photometer or respectivelyspectrometer without further change of the light path.

The pincette 9 may feature an introducing aid, which permits a simple“filling” of the measuring areas 4, 5. In the opened condition, the arms7, 8 of the pincette stand towards other such, that a sufficiently largespace is provided for applying the sample, for instance in the form of adrop, onto one of the planar measuring areas 4,5. By pushing togetherthe two arms 7, 8, the planar measuring areas 4, 5 on the ends of thearms 7, 8 are moved towards each other, so that the drop wets bothmeasuring areas 4, 5. In this, the planar measuring areas 4, 5 can beshaped and/or coated such that the direction of spreading of the mediumtowards the measurement direction is favoured, and that when it isoverdosed, it can escape only in one direction, for instance towards thetopside. By the two spacer parts 11, 12, preferably situated near to theplanar measuring areas 4, 5, the arms 7, 8 are positioned such that adefined optical layer thickness between the measuring areas 4, 5 isgenerated. Measurements with volumes from one micro-litre up to severalmicro-litres can be realised in one adapter 6 by means of differentpincettes 9 having different layer thicknesses.

In addition, the pincette 9 may contain a locking function which permitsthe user to leave the pincette from his/her hand in the closed state, inwhich the spacer parts 11, 12 sit close to each other.

Furthermore, the pincette may contain alignment devices in addition,which align the measuring areas 4, 5 in parallel.

In its closed condition, the pincette 9 is inserted into the guide rails19 to 22 of the adapter 6, until the bevels of the arms 7, 8 abutagainst the inclined limitation walls 23, 24 of the adapter. In thisposition, the platelets 2, 3 are arranged vertically in the adapter 6,and are directed towards the passage openings 26, 27 with their outersides. The pincette 9 can be kept in the closed condition by the guiderails 19 to 22.

When the adapter 6 is arranged in the cuvette shaft of a photometer orspectrometer, the passage openings 26, 27 are arranged in the beam pathof the measuring optics, so that the same can be used for the opticalmeasurement of the sample between the measuring areas 4, 5.

The adapter 6 can be realised such that any leakage of the liquid sampleupon mistreatment, at shocks for instance, is prevented. Moreover, itcan have the features of a stop, by which an universal utilisation notdepending on the type of the spectrometer is possible. The adapter 6 canbe realised as a disposable item like a cuvette, but replacement isnecessary only in the case of mistreatment.

The cuvette of FIGS. 5 to 8 is not subject matter of the presentinvention, it is described only for illustrating the claimed invention.

The cuvette according to FIGS. 5 to 8 consists of at least twocomponents, namely of a measurement point 28 and an adapter 29. Themeasurement point 28 has an upper end with an upper opening 30, by whichit can be clamped onto a fastening neck of for instance a currentlymarketed pipette. Further, it has a bottom end with a bottom opening 31.This bottom opening 31 is limited by a device 1, comprising twotransparent platelets 2, 3 having planar and preferably plane-parallelmeasuring areas 4, 5 at the inner sides. The distance region between theplatelets 2, 3 is laterally closed, so that the distance region is openonly on the bottom side at 31.

A continuous channel is formed in the measuring point 28 between theupper opening 30 and the lower opening 31. At the outside, the measuringpoint 28 has a form that tapers from the topside to the bottom side.

The adapter 29 is also box-like and matched to a standard cuvette shaft.In the upper region 32, it is closed on the circumference, and on thedownside it has four feet 33 to 36.In the interior, the adapter 29 has acavity 37, in which an accommodation 38 is arranged. The accommodation38 is matched to the outer contour of the measurement tip 28. At theinside, the accommodation 38 is supported on the walls of the adapter 29via radially running ribs 39, 40, 41, 42.

The measuring point 28 can be put up onto a fastening neck of e.g. anusual commercial pipette, like a conventional pipette point, by way ofwhich the medium to be measured can be sucked in between the platelets2,3. In doing so, the medium wets the planar measuring areas 4, 5.Measuring reservoirs of different magnitude for measurements havingvolumes of less than one micro-litre up to several micro-litres ordifferent layer thicknesses, respectively, can be realised in onecuvette by way of different measuring points 28 with different distancesbetween the measuring areas 4, 5. In embodiments for the measurement ofvery small volumes in particular, the sample to be measured can be drawnbetween the plates 2, 3 by the capillary forces already. Picking up thesample with the aid of for instance a commercially available pipette isthen no more necessary.

The filled measuring point 28 is put into the adapter 29 with the aid ofa pipette. The shape of the accommodation 38 is matched to the shape ofthe measuring point 28, such that the inserted measuring point isarranged with the platelets 2, 3 in the free spaces between the feet 33to 36. The cuvette 29 can then be put into a cuvette shaft with themeasuring point 28 being put in, so that the light path of the opticalmeasurement device runs between opposing free spaces between the pairsof feet 33, 34 and 35, 36 and crosswise through the two platelets 2, 3and the sample situated therein. Picking up the sample is favoured byhydrophilic surfaces.

The adapter 29 can be realised such that leakage of the liquid to bemeasured upon wrong handling—at too strong a shock for instance—isprevented. Furthermore, it can serve as a guiding mechanism for thecorrect alignment of the planar measuring areas 4, 5 with respect to themeasurement direction of the photometer. Further, it may have the natureof a stop, by which a universal utilization independent of thespectrometer's type is possible.

Measuring point 28 and adapter 29 can each be realised as consumables.The measuring point 28 can be replaced after each measurement.Replacement of the adapter 29 can be limited to cases of wrongtreatment.

The following two realisation examples comprise two collapsible adapterparts, which are preferably captively connected to each other via anarticulation. In a collapsed condition, the adapter parts form anadapter, with the dimensions of e.g. a standard cuvette. Thearticulation may be attached on the short or on the long side of thedevice. Swung apart, the sample to be measured is applied to only one orto both measuring areas.

The cuvette according to FIGS. 9 to 12 comprises two plate-shaped samplecarriers (“slides”) 43, 44 and an adapter 45. The sample carriers 43, 44are identical. The have an enlarged grip and path stop 47 on the upperend of a strip-shaped centre part 46. At the downside, the strip-shapedcentre part 46 tapers conically at 48. On the lower end, each of theslides 43, 44 has a platelet 2, 3 with the planar measuring area 4respectively 5, preferably on one side.

The adapter 45 comprises two adapter parts 49, 50, which arearticulatedly connected to each other via a film hinge 51. In acollapsed condition, the adapter parts 49, 50 according to FIG. 12 forman adapter 45, whose form corresponds essentially to that of the adapter6 according to FIGS. 3 and 4. However, in difference to the adapter 6,the adapter 45 has a complete guiding mechanism consisting of four guiderails 52 to 55 and 56 to 59 in each one of both adapter parts 49, 50.

The adapter 45 and the slides 43, 45 are preferably made of plastics.

According to FIG. 11, two slides 43, 44 are inserted into the guidingmechanisms 52 to 55 and 56 to 59, until the grip and path stop 47 findsrest on the upper border of the two adapter parts 49, 50. In thisposition, the platelets 2, 3 are disposed in recesses between feet 60,61 of the adapter part 49, and 62, 63 of the adapter part 50. Further, acatch lock of the slides 43, 44 with the guiding mechanisms 52 to 55 and56 to 59 can be provided.

Then, one drop of the liquid to be measured is applied to the planarmeasuring area 4. Thereafter, the two adapter parts 49, 50 are swungtogether, whereby the liquid comes into contact with the measuring area5.

The collapsed adapter parts 49, 50 are locked with each other by way ofa catching hook 64 having a catching recess 65 on the adapter part 50,and a catching projection 66 on the adapter part 49. In this, thecatching hook 64 is pushed onto the catching projection 66 with itscatching recess 65. By actuating the catching hook 64 in the oppositedirection, the locking can be released.

According to FIG. 12, the closed adapter 45 can be put into a standardcuvette shaft, wherein the beam path of the optical measuring devicecrosses the two platelets 2, 3 through the recesses between the feet 60,61 and 62, 63.

In the cuvette according to FIGS. 9 to 12, the arms or respectivelyadapter parts 49, 50 are articulated to each other along a long side. Inthe cuvette according to FIGS. 13 and 14, the arms or respectivelyadapter parts 67, 68 have an articulated joint 69 along a transversalaxis.

For this purpose, the adapter part 67 has a plate-shaped base part 70,which has two bridges 71, 72 at its upper region on one side at theoutside. Bearing eyes 73, 74 of the revolution joint 69 are arranged inthe bridges 71, 72.

In principle, the adapter part 68 consists of a plate-shaped carrierpart 75, which is connected to one end of a connection arm 76, whichcarries a bearing block 77 at its other end. The bearing block 77 isarranged between the legs 71, 72, an axis or shaft 78 being guidedthrough a central passage bore of the bearing block 77 and being held inthe bearing eyes 73, 74 on both ends.

The base part 70 and the carrier part 75 have passage openings 79, 80,which are in true alignment with each other in the collapsed conditionof the adapter parts 67, 68. On the inner sides of the passage openings79, 80 sit plate-shaped insert parts 81, 82 with planar measuring areas83, 84 on their inner sides.

Preferably, the base part 70 and the carrier part 75 each have magnets85 to 88 and 89 to 92, each inserted in the inside, which sit pairwiseclose to each other in the collapsed condition. Further, a centring pin93 projects from the base part 70, to which is associated a centringaccommodation 94 of the carrier part 75.

It is advantageous to adjust the distance between the measuring areas83, 84 via the magnet pairs in the manufacture of the cuvette. This mayfor instance be achieved by setting the magnets 85 to 92 into adhesivebeds. These are allowed to harden when the cuvette is in a closedcondition, the correct alignment of the magnets 85 to 92 being made sureby a locating piece that is inserted between the measuring areas 83, 84.At option, the adhesive bed of one magnet 85 to 92 at a time of eachpair can be hardened already before closing. In order to design thesystem without remaining degrees of freedom, but not in anoverdetermined fashion, it is advantageous to use three pairs ofmagnets. In addition, for the same reason it is advantageous to designthe revolution joint 69 of the cuvette floatingly, i.e. with clearance,with respect to the axis vertical to the measuring areas 83, 94.

A sample can be applied to one or both planar border surfaces 81, 82 inthe opened condition of the adapter. After collapsing the adapter parts67, 68, the adapter is insertable into a standard cuvette shaft. Thelight path of the optical measuring device passes through the passageopenings 79, 80, the transparent platelets 81, 82 arranged behind themand the sample situated there between.

The insert parts 81, 82 are for instance made of UV-permeable quartzglass or UV-permeable plastics. As the case may be, they are providedwith a special surface structure.

The borders of the passage openings 80, 81 form stops, which effect thatthe measuring light of the photometer or spectrometer irradiates onlythrough the sample. The adapter parts 67, 68 are preferably made ofplastics.

The adapter parts 67, 68 may be made of another material, of metal forinstance, in particular when they are destined for re-use. In a furthervariant, the adapter parts 67, 68 may consist of the same plastics likethe insert parts 81, 92, and as the case may be, they may be producedinseparably as one single injection moulded object.

In particular, the cuvette can be made such that a gap remains aftercollapsing it, via which the region between the measuring areas 83, 84can be inspected. This can be used in order to fill the cuvette in itsclosed condition. In order to facilitate filling, the gap can beenlarged with a recess in the direction towards the measuring areas.

Another variant, which permits to fill the cuvette in the closedcondition, is shown in FIGS. 13.1, 14.1 and 14.2. When filling thecuvette in the closed condition, both measuring areas 83, 84 are wettedat the same time. This has the advantage that a smaller volume is neededin order to produce a liquid bridge between the measuring areas 83, 84.Besides to this, the evaporation of the sample during the handling canbe prevented by doing so.

In FIGS. 13.1, 14.1 and 14.2, those elements that correspond to elementsof the embodiment of FIGS. 13 and 14 are designated with the samereference signs, but which are indicated by a superscripted dash (′).

In order to fill it in the closed condition with the aid of a pipette,the embodiment of FIGS. 13.1, 14.1 and 14.2 has a recess 125 in the arm67 which extends on the free end of the arm 67′ from out its outer side126 up to the measuring area 83′. The slot-like recess 125 is shaped anddimensioned such that the lower end of the pipette point 127 fits intoit and is laterally guided therein. Further, the insert part 81′ isarranged somewhat nearer to the revolution joint 69′ than the insertpart 82′, so that the sample can be metered directly onto the measuringarea 84′ and into the interstice between the measuring areas 83′, 84′ byway of the pipette point 127.

In this embodiment, the insert parts 81, 82′ are made strip-shaped anddetachably or fixedly connected to the arms 67′, 68′. The revolutionjoint 69′ is made as a floating hinge, for instance by arranging theaxle or shaft 78′ either in a passage opening with oversize of thebearing block 77′ and pressing it into the bearing eyes 73′, 74′, or bypressing it into the passage bore and arranging it in the bearing eyes73′, 74′ that have oversize. Further, this embodiment has three pairs ofmagnets 85′ to 87′ and 89′ to 91′ for locking the arms 67′, 68′ in themeasuring position.

According to FIGS. 15 and 16, the optically transparent measuring areas83, 84 are realised so as to have a central liquid-wetting surfaceportion 95, around which there is a liquid-repellent surface portion 96.The liquid-wetting and liquid-repellent properties of the regions 95, 96can be produced by coatings. Between the two surface portions 95, 96there is no mechanical edge which would disturb when the measuring areas83, 84 are being cleaned. The measuring areas 83, 84 are cleanedstarting from the surface portion 95 and towards the surface portion 96,so that no residual contaminations remain in the central surface portion95.

A light-permeable surface portion 97 corresponds to the liquid-wettingsurface portion 95, and a light-impermeable surface portion 98 on theouter side of the insert part 83, 84 corresponds to the liquid-repellentsurface portion.

The surface portions 95, 96 limit the spreading of the liquid sample onthe measuring areas 83, 84. On the liquid-repellent respectivelyhydrophobic surface portion, the drop of liquid has a great contactangle point. Due to this, it projects far above the measuring areas 83,84. However, in the liquid-wetting respectively hydrophilic surfaceportion 95, the drop is retained or anchored, respectively. Due to this,there arise no flat, but approximately semi-globular drops of liquid, sothat when collapsing the adapter parts 67, 68, a drop that is applied toa measuring area 83 or 84 securely wets the other measuring area 84, 83,or other drops applied to both measuring areas 83, 84 securely unitewith each other. As a consequence, there arises a defined column ofliquid, and through this a defined measurement path or layer thickness,respectively.

The platelets 2, 3 of the remaining realisation examples can be realisedcorrespondingly on the measuring areas 4, 5 and the outer sides.

In the realisation example according to FIGS. 17 to 20, differentlyshaped deepenings 99, 100, 101, 102 are arranged in the measuring areas83, 84. The deepenings 99 to 102 accommodate samples and limit thespreading thereof on the measuring areas 83, 84. According to FIGS. 18and 19, excess amount of sample can escape into reservoirs 104 viaradial channels 103, or into an overflow chamber 106 via an overflowedge 105. In the realisation example of FIG. 20, the deepening 102 isconically enlarged towards the outside. In addition, the border surface107 that limits the extension can be liquid-repellent, and the basesurface 108 liquid-wetting, so that the drop projects from the measuringarea 83, 84 as far as possible.

In order to limit the drop spreading, a planar pedestal having a smallsurface area can also be arranged on the measuring area 83, 84. Theplanar pedestal prevents the spreading of the drop due to its surfacetension. This results in an increase of the drop height, and a reductionof the necessary amount of sample can be achieved.

The form of the measuring areas according to FIGS. 17 to 20 or with apedestal can be realised in all embodiments.

According to FIGS. 21 and 22, the thickness of the layer between the twomeasuring areas 4, 5 can be defined by a spacer ring 109. A stop 110 isapplied as a coating on the outer side of the platelet 3.

In this example, a drop is applied only to measuring area 5, which wetsthe measuring area 4 upon close contact with the spacer ring 9.

In the realisation example according to FIGS. 23 and 24, spacer rings111, 112 are assigned to both measuring areas 4, 5, which come intocontact with each other when the device is closed. In this example, thelayer thickness is defined by both spacer rings 111, 112. Further shownis the application of drops onto both measuring areas 4, 5, whichcoalesce when the device 1 is closed.

The realisation example of FIG. 25 differs from that according to FIGS.21 and 22 in that the defined layer thickness is preferably ensured bymagnetic forces from magnets 113, 114, 115, 116, whose unlike poles arearranged in a short distance from each other when the device 1 isclosed. The magnets 113 to 116 are integrated into device components(for instance adapter parts 67, 68) of the cuvette, which accommodatethe inserts 2,3.

In order to ensure the plane-parallel alignment of the measuring areas4, 5, a hinge 69 that is formed between the device components 67, 68 canbe made to float, so that the system is not geometricallyoverdetermined. In the closed condition, the sample to be measured ispositioned definedly, safely and stably in the collapsible cuvette whichhas two adapter parts 67, 68.

A further embodiment of the present invention represents magazining ofthe single-use items and is not shown in detail. From an easy to handlemagazine, preferably in the form of a cartridge, the inserts 2, 3 forsingle-use can be inserted easily into the openings of a re-usablecollapsible cuvette which are provided for this purpose. After use, thesingle-use inserts 2, 3 are pushed out of the collapsible adapter byhand or by way of a device or by way of a lug on the cartridge, and thenthrown away. New inserts 2, 3 may then be inserted again.

The single-use items can also be combined with adapters that arerealised as single-use items. Further possible is a combined single-useitem with front and rear part from one tool, as the case may be also asa so-called two component injection moulded article.

The cuvette of FIGS. 26 to 28 is not subject matter of this application.It is described only for the sake of illustration of the claimedinvention.

The cuvette according to FIGS. 26 to 28 corresponds to a great extent tothe cuvette according to the realisation example of DE 198 26 470 C1,which is incorporated by reference. However, in difference to the knowncuvette, the box-like bottom part 121, arranged between the four feet117, 118, 119, 120, is not opened at the inside towards a cavity of thecuvette, but is closed instead. Further, a channel 122, open towardsboth sides, runs through this bottom part 121, which has funnel-shapedexpansions 123, 124 towards both outer sides.

The cuvette has the shape of a commercially available cuvette, so thatit can be put into a conventional commercial photometer or spectrometer,respectively.

Crossing the channel 122 which is open on both sides, opticalmeasurements can be performed. Through this, no light is guided througha plastics wall of the cuvette during the measurement, and thus, themeasurement is not influenced. It is not necessary to measure a valuefor each empty cuvette.

The channel 122 tapers conically towards the outer sides of the cuvette,so that an overdosage results only in a marginal increase of the opticallayer thickness. As a side effect, the cuvette receives a filling aidthrough this. A pipette point can be put on the expansions 123, 124 andthe channel 122 be filled in this way, until the liquid reaches from theboarder between the conical and the cylindrical region of the channel122. Now, the liquid completely fills the channel 122 and is heldtherein by adhesion or capillary action, respectively.

The conical expansions 123 can be made rough, on the one hand forachieving the stop effect, and on the other hand in order to avoidleaking of the liquid upon wrong handling. In addition to this, a troughcan then be provided below the channel 122, which can receive the liquidthat leaks out. As the channel 122 is significantly shorter than theoverall width of the cuvette, the liquid can fall down only into thistrough.

In the realisation example of FIGS. 29 and 30, elements that correspondto elements of the realisation example of FIGS. 1 to 4 are provided withthe same reference numerals, but in addition marked by a superscripteddash (′).

The insert 1′ is also realised in the kind of a pincette, whereinhowever, the arms 7′, 8′ are connected to each other on their upper endsby a film hinge 128.

Each strip-shaped arm 7′, 8′ has a shoulder 129, 130 or respectively aflattening at one end, in which the measuring areas 4′, 5′ are arranged.Each of these measuring areas 4′, 5′ has a group (6 in the example) ofcircular area portions 131, 132 for receiving sample liquid. One pair ata time of the area portions 131, 132 faces each other, so that itoverlaps when the arms 7′, 8′ are swung together.

The area portions 131, 132 can be delimited from the rest of themeasuring areas 4′, 5′ in that they are arranged deeper in littledeepenings.

According to another embodiment, the area portions 131, 132 are arrangedin deepenings and the area portions and the further area portions 133,134 of the measuring areas 4′, 5′ which surround them have a hydrophobiccoating. According to another embodiment, in which the area portions131, 132 are not arranged in deepenings, the area portions 131, 132 havea hydrophilic coating, so that the samples are held thereon. Accordingto another embodiment, in which the area portions are not arranged indeepenings, the further area portions 133, 134 of the measuring areas4′, 5′ that surround them and which should not receive sample, have ahydrophobic coating. According to another embodiment, in which the areaportions are not arranged in deepenings, the area portions 131, 132 havea hydrophilic coating and the further area portions 133, 134 thatsurround them have a hydrophobic coating.

When the arms 7′, 8′ are swung together, samples put on the areaportions 131, 132 of the measuring areas 4′, 5′ are spanned up betweenthe same.

Further, the arms 7′, 8′ each have a group of parallel grooves 135, 136at the outer sides, which extend crosswise to their longitudinal axis.The grooves 135, 136 are disposed near to the free ends of the arms 7′,8′. In the example, the grooves 135, 136 on the different arms 7′, 8′are disposed at equal distances from the free ends of the arms 7′, 8′.In another embodiment, which is not shown, the grooves 135, 136 on thedifferent arms 7′, 8′ are disposed at different heights. In stillanother embodiment, which is not shown, only one of the arms 7′, 8′ hasgrooves 135 or 136, respectively.

The insert 1′ is made in one piece of plastics. Due to the elasticity ofthe film hinge 128, it takes on the configuration of FIG. 29automatically.

The adapter 6′ has the cuboid outline of a standard cuvette. It isessentially cuboid. It has an accommodation 137 with rectangular crosssection, into which the insert 1′ can be put in from the topside whenthe arms 7′, 8′ are swung together. An elastically acting projection 148of the adapter 6′ engages into the accommodation 137, which engages intoone of the grooves 135 or 136 of the inserted insert 1′. Through this,the insert 1′ is caught in the accommodation 137 in a height position.

The elastic catching projection 138 is realised as a small wheel, whichis rotatably mounted at the end of a spring tongue 139. The springtongue 139 is disposed in a longitudinal slot 140 of a side wall 141 ofthe adapter 6; and fixed at the lower end by way of a screw 142. As aconsequence, the spring tongue 139 can be deflected within thelongitudinal slot 140. The spring tongue 139 is deflected when thecatching projection 138, realised as a small wheel, rolls over the outerside of an arm 7′, 8′. Finally, the catching projection 138 falls intoone of the grooves 135, 136, and through this, the insert 1′ is fixed inthe adapter 6′ at a certain height.

On opposing side walls 141, 142, the adapter 6′ has passage openings26′, 27′ for the beam path of an optical measuring device. The passageopenings 26′, 27′ are arranged in the lower third of the side walls 141,142, approximately on the centre axis of the same.

In the catching position shown in FIG. 30, the area portions 131, 132,which are situated in FIG. 29 at the right downside on the measuringareas 4′, 5′ on the arms 7′, 8′, are arranged exactly between thepassage openings 26′, 27′. When the adapter 6′ with the insert 1′ is putinto a cuvette shaft in this catching position, a sample can be measuredbetween these area portions 131, 132 of the measuring areas 4′, 5′. Inthe next deeper catching position, that sample moves into the beam pathwhich is situated between the middle area portions 131, 132 of the rightrow, and so forth.

By pulling out the insert 1′ from the accommodation 137, turning itabout 180° around its longitudinal axis and putting it into theaccommodation 137 anew, the samples between the area portions 131, 132,which are situated on the measuring areas 4′, 5′ on the arms 7′, 8′ inthe left row at the downside in FIG. 29, can be brought into the beampath.

In another embodiment, filling the insert 1′ when the arms 7′, 8′ areswung together is favoured in that the arms 7′, 8′ have small openingsor respectively guiding mechanisms for a pipette on the two lateralborders of the measuring areas 4′, 5′, which extend from the lateralborders to the area portions 131, 132. A pipette point can be put intothe openings or respectively guiding mechanisms, so that samples can beapplied to the area portions 131, 132 of the collapsed measuring areas4′, 5′ by way of a pipette.

The described realisation examples serve for illustrating the invention.However, the present invention is not limited to the realisationexamples.

This completes the description of the preferred and alternateembodiments of the invention. Those skilled in the art may recognizeother equivalents to the specific embodiment described herein whichequivalents are intended to be encompassed by the claims attachedhereto.

1. Cuvette, comprising at least one measuring area (4, 5, 83, 84) oneach one of two arms (7, 8, 67, 68) that are pivotally connected to eachother, such that from a swung-apart condition, they can be swungtogether into a measuring position in which the two measuring areas (4,5, 83, 84) have a distance for positioning a sample between themeasuring areas (4, 5, 83, 84), and means for positioning the two arms(7, 8, 67, 68) in a measuring position in a cuvette shaft of an opticalmeasuring device with a sample between the two measuring areas (4, 5,83, 84) in a beam path of the optical measuring device that crosses thecuvette shaft, wherein the means for positioning the two arms (7, 8, 67,68) have a shape that is adapted to the cuvette shaft.
 2. Cuvetteaccording to claim 1, with means for positioning the two arms (7, 8, 67,68) disposed in the measuring position in a standard cuvette shaft. 3.Cuvette according to claim 1, with means for positioning the two arms(7, 8, 67, 68) disposed in the measuring position in different positionsin a cuvette shaft
 4. Cuvette according to claim 3, with means forpositioning the two arms (7, 8, 67, 68) disposed in the measuringposition in different height positions and/or different horizontalpositions in a cuvette shaft.
 5. Cuvette according to claim 1, whereinthe means for positioning have a cross section of the arms (7, 8, 67,68) swung together in the measuring position which is adapted to thecuvette shaft.
 6. Cuvette according to claim 1, wherein the two arms (7,8, 67, 68) are pivotally linked to each other via an articulation (69)7. Cuvette according to claim 6, wherein the articulation (69′) is afloating articulation.
 8. Cuvette according to claim 1, which has meansfor preventing the swinging together of the arms in the measuringposition, and/or which has means for detachably locking (85 to 88, 89 to92) the two arms (67, 68) in the measuring position.
 9. Cuvetteaccording to claim 1, which has the two measuring areas (83, 84) on twoinsert parts (81, 82) and which has means for detachably or notdetachably holding the two insert parts on the arms (67, 68). 10.Cuvette according to claim 1, wherein at least one arm (67′) has arecess (125), extending from the outer side of the arm (67′) up to themeasuring area (83′), for inserting a pipette point (127) and putting asample between the measuring areas (83′, 84′) in the measuring position.11. Cuvette according to claim 1, wherein an insert (1) features the twoarms (7, 8) with the two measuring areas (4, 5), and the means forpositioning feature an adapter (6) for insertion into the cuvette shaft,and means of insert and adapter for detachably holding the insert (1) inthe adapter (6), the measuring areas (4, 5) being in a distance fromeach other, for positioning a sample between the measuring areas (4, 5).12. Cuvette according to claim 11, wherein the insert (1) is a pincettehaving the two measuring areas (4, 5) on the free ends of the arms (7,8).
 13. Cuvette according to claim 11, wherein the arms (7, 8) of theinsert (1) taper towards the free ends.
 14. Cuvette according to claim11, wherein the insert (1) has means for preventing the swingingtogether of the arms in a measuring position in which the two measuringareas (4, 5) have a certain distance from each other, and/or means fordetachably locking the two arms (7, 8) in the measuring position. 15.Cuvette according to claim 11, wherein the means for detachably holdingcomprise an accommodation of the adapter (6) and a contour of the insert(1) whose geometries are matched such that the insert in insertable intothe accommodation into at least one certain position.
 16. Cuvetteaccording to claim 15, wherein the adapter (6′) and the insert (1′) havecatching means (129, 130) for detachably holding the insert (1′) indifferent positions in the accommodation (131) of the adapter (6′). 17.Cuvette according to claim 15, wherein the accommodation (131) isdisposed asymmetrically with respect to the outline of the adapter (6′).18. Adapter (4, 5) for at least one insert with at least one measuringarea on each of two arms (7, 8) that are pivotally connected with eachother, wherein the adapter (6) is insertable into a cuvette shaft of anoptical measuring device and has means for detachably holding the atleast one insert (1), so that the arms (7, 8) are swung together in ameasuring position in which the measuring areas are in a distance fromeach other, and for positioning a sample between the measuring areas ina beam path of the optical measuring device that crosses the cuvetteshaft.
 19. (canceled)
 20. Cuvette according to claim 1, wherein the twomeasuring areas (83, 84) and/or insert parts (81, 82) are opticallytransparent.
 21. Cuvette according to claim 1, wherein the two measuringareas (83, 84) and/or insert parts (81, 82) are platelet-shaped. 22.Cuvette according to claim 1, wherein at least one measuring area (83,84) or at least one insert part (81, 82) are made of plastics or quartzglass or glass and/or at least one arm and/or the insert and/or theadapter are made of plastics and/or metal.
 23. Cuvette according toclaim 1, wherein at least one measuring area (83, 84) has a planarpedestal.
 24. Cuvette according to claim 1, wherein at least onemeasuring area (83, 84) has a deepening.
 25. Cuvette according to claim1, wherein at least one measuring area (83, 84) is hydrophobic. 26.Cuvette according to claim 1, wherein at least one measuring area (83,84) is hydrophilic.
 27. Cuvette according to claim 25, wherein at leastone measuring area (83, 84) has a less hydrophobic or hydrophilic spot.28. Cuvette according to claim 1, wherein the measuring areas (83, 84)are planar.
 29. Cuvette according to claim 1, wherein the measuringareas (83, 84) are disposed in parallel in the measuring position. 30.Cuvette according to claim 1, wherein the distance of the measuringareas (83, 84) from each other is about 1 mm in the measuring position.31. Cuvette according to claim 1, wherein the distances between the twomeasuring areas (83, 84) are dimensioned such that the volumes of thesamples are 0.2 to 5 micro-litres.
 32. Cuvette according to claim 1,which has at least one stop for limiting a light beam through themeasuring areas (83, 84).
 33. Method for the optical examination ofsmall amounts of liquid, wherein two measuring areas arranged at adistance from each other are wetted with several liquid samples, so thatthe drops are spanned out between the measuring areas through theirsurface tension, and the drops are subjected to one or several opticalmeasurements.
 34. Method according to claim 33, wherein the opticalmeasurement is performed across open sides of the distance regionbetween the measuring areas or the interstice.
 35. Method according toclaim 33, wherein the interstice has at least one transparent wall, andthe optical measurement is performed across the transparent wall. 36.Method according to claim 33, wherein plural liquid samples are examinedsimultaneously.